Baja Triode Emulator Boost Plus

bajaman · Post by **bajaman** » 03 Jul 2008, 12:42

Hello Dimitri

thanks for dropping by and thanks for the suggestions.
Another forum member and I exchanged emails regarding the current to voltage conversion stage a while back and we were both puzzled by the configuration - any help with analysing it would be appreciated.
Thank you for such a great design idea - i must get back to it when i get some more free time.
cheers
bajaman

PierreBPSFSB · Post by **PierreBPSFSB** » 23 Mar 2010, 18:13

Hello !
- I am impressed by this schematic !

- If it is not too late, i would appreciate if Bajaman could email me the AES2004 paper of Dimitri (Hello !), to improve my knowledge !

- I made some Spice simulations & Proto of Jfet cascode, ActiveLoad etc.. but i never saw that (about Ao2 + Ao3 Loop around the JFet !).
In my understanding, to complete as Baracuda said, it is like a HiGain DCloop to "DC"Feedback the Jfet Drain at +Vcc/2: the output of the loop (via R=100) is a Voltage to Current source (seems Integrator+Rsense modified Howland) which feeds an +Vbias with "AC very lowZin" at the AOe-/DrainFet point, to cancel the Miller Effect, but mainly in order to Adjust the AC Gain of this stage (Jfet+Ao2) via 10K Trim Without changing the Ao2 Vout DC Idle @ +1/2Vcc: this ensure that the Ao will never "disturb" the wanted JFET non-linearity.
- Its some thoughts !

matt239 · Post by **matt239** » 24 Jun 2011, 14:55

Hotrats wrote: .... with source resistance equal to zero (max curvature) the Vin=0 point coincides with Vgs=0 unless there is something additional in the source circuit to shift the response. pretty obvious what that can be.

I built several cascaded versions using my way of shifting and I get wicked compression from the circuit - to do this you also need to up the voltage gain with and extra stage in each element (similar to Dannyuk's op-amp) making sure the range of curvature is allowed to happen within the range of the output device - this means biasing the stage so it's idling close to the rail and allowed to down expand far enough to get a good cross-section of the parabola. When you get enough of the parabola happening and you cascade to such stages the exagerated lobe will act to shut off the following stage - hence the compression effect. ...

I see that it's been a while, but if you're still following, can you explain/expand on this?
Or, can anyone else comment?

guillernofear · Post by **guillernofear** » 11 Sep 2013, 02:09

Bajaman Hi, thanks for the schematic and PCB, I've built and sounds great as audio preamplifier also thanks for all, greetings from Argentina

mganzer · Post by **mganzer** » 23 Oct 2013, 19:47

Hi guys;
What is the voltage of v+, 1/2V and vbias? I want to manage power without charger pump... (maybe using a diodes/caps arrange to double the voltage and put some extra filtering)
If i want to cut off the buffer out, the 2u2 cap, 100k and 560r are useless, right?
How much drive it can generates? some diodes to ground clipping after the last opamp(boost control) is a bad idea? or some bat 41 in the negative feedback in this same opamp?
Can i put the amz stupidly wonderful tone control at the end to get control of volume and tone?
Two lf353 can substitute the tl084?
Thank you.

bajaman · Post by **bajaman** » 15 Sep 2019, 20:38

Here are the missing images (no thanks to Photofuckit

) from the original post.
cheers
bajaman

Jmpj48 · Post by **Jmpj48** » 15 Sep 2019, 20:47

Thanks for the schematic baha greatly appreciated.

melonmelon · Post by **melonmelon** » 04 Mar 2021, 21:48

Hi Bajaman - any 2SK117 will work properly?

Baja Triode Emulator Boost Plus [documentation]